From: Tom Lendacky Date: Wed, 5 Jun 2024 15:18:51 +0000 (-0500) Subject: virt: sev-guest: Choose the VMPCK key based on executing VMPL X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=eb65f96cb332d577b490ab9c9f5f8de8c0316076;p=users%2Fjedix%2Flinux-maple.git virt: sev-guest: Choose the VMPCK key based on executing VMPL Currently, the sev-guest driver uses the vmpck-0 key by default. When an SVSM is present, the kernel is running at a VMPL other than 0 and the vmpck-0 key is no longer available. If a specific vmpck key has not be requested by the user via the vmpck_id module parameter, choose the vmpck key based on the active VMPL level. Signed-off-by: Tom Lendacky Signed-off-by: Borislav Petkov (AMD) Link: https://lore.kernel.org/r/b88081c5d88263176849df8ea93e90a404619cab.1717600736.git.thomas.lendacky@amd.com --- diff --git a/Documentation/virt/coco/sev-guest.rst b/Documentation/virt/coco/sev-guest.rst index e1eaf6a830ce4..9d00967a5b2b5 100644 --- a/Documentation/virt/coco/sev-guest.rst +++ b/Documentation/virt/coco/sev-guest.rst @@ -204,6 +204,17 @@ has taken care to make use of the SEV-SNP CPUID throughout all stages of boot. Otherwise, guest owner attestation provides no assurance that the kernel wasn't fed incorrect values at some point during boot. +4. SEV Guest Driver Communication Key +===================================== + +Communication between an SEV guest and the SEV firmware in the AMD Secure +Processor (ASP, aka PSP) is protected by a VM Platform Communication Key +(VMPCK). By default, the sev-guest driver uses the VMPCK associated with the +VM Privilege Level (VMPL) at which the guest is running. Should this key be +wiped by the sev-guest driver (see the driver for reasons why a VMPCK can be +wiped), a different key can be used by reloading the sev-guest driver and +specifying the desired key using the vmpck_id module parameter. + Reference --------- diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h index 1d0b1b23fafba..9c6f269d4bf55 100644 --- a/arch/x86/include/asm/sev.h +++ b/arch/x86/include/asm/sev.h @@ -237,6 +237,9 @@ struct svsm_call { #define SVSM_CORE_DELETE_VCPU 3 #ifdef CONFIG_AMD_MEM_ENCRYPT + +extern u8 snp_vmpl; + extern void __sev_es_ist_enter(struct pt_regs *regs); extern void __sev_es_ist_exit(void); static __always_inline void sev_es_ist_enter(struct pt_regs *regs) @@ -319,7 +322,10 @@ u64 snp_get_unsupported_features(u64 status); u64 sev_get_status(void); void sev_show_status(void); void snp_update_svsm_ca(void); -#else + +#else /* !CONFIG_AMD_MEM_ENCRYPT */ + +#define snp_vmpl 0 static inline void sev_es_ist_enter(struct pt_regs *regs) { } static inline void sev_es_ist_exit(void) { } static inline int sev_es_setup_ap_jump_table(struct real_mode_header *rmh) { return 0; } @@ -349,7 +355,8 @@ static inline u64 snp_get_unsupported_features(u64 status) { return 0; } static inline u64 sev_get_status(void) { return 0; } static inline void sev_show_status(void) { } static inline void snp_update_svsm_ca(void) { } -#endif + +#endif /* CONFIG_AMD_MEM_ENCRYPT */ #ifdef CONFIG_KVM_AMD_SEV bool snp_probe_rmptable_info(void); diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c index 2f509109c4f25..71de531940891 100644 --- a/arch/x86/kernel/sev-shared.c +++ b/arch/x86/kernel/sev-shared.c @@ -36,7 +36,8 @@ * early boot, both with identity mapped virtual addresses and proper kernel * virtual addresses. */ -static u8 snp_vmpl __ro_after_init; +u8 snp_vmpl __ro_after_init; +EXPORT_SYMBOL_GPL(snp_vmpl); static struct svsm_ca *boot_svsm_caa __ro_after_init; static u64 boot_svsm_caa_pa __ro_after_init; diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c index 654290a8e1ba3..4597042f31e45 100644 --- a/drivers/virt/coco/sev-guest/sev-guest.c +++ b/drivers/virt/coco/sev-guest/sev-guest.c @@ -2,7 +2,7 @@ /* * AMD Secure Encrypted Virtualization (SEV) guest driver interface * - * Copyright (C) 2021 Advanced Micro Devices, Inc. + * Copyright (C) 2021-2024 Advanced Micro Devices, Inc. * * Author: Brijesh Singh */ @@ -70,8 +70,15 @@ struct snp_guest_dev { u8 *vmpck; }; -static u32 vmpck_id; -module_param(vmpck_id, uint, 0444); +/* + * The VMPCK ID represents the key used by the SNP guest to communicate with the + * SEV firmware in the AMD Secure Processor (ASP, aka PSP). By default, the key + * used will be the key associated with the VMPL at which the guest is running. + * Should the default key be wiped (see snp_disable_vmpck()), this parameter + * allows for using one of the remaining VMPCKs. + */ +static int vmpck_id = -1; +module_param(vmpck_id, int, 0444); MODULE_PARM_DESC(vmpck_id, "The VMPCK ID to use when communicating with the PSP."); /* Mutex to serialize the shared buffer access and command handling. */ @@ -923,6 +930,10 @@ static int __init sev_guest_probe(struct platform_device *pdev) if (!snp_dev) goto e_unmap; + /* Adjust the default VMPCK key based on the executing VMPL level */ + if (vmpck_id == -1) + vmpck_id = snp_vmpl; + ret = -EINVAL; snp_dev->vmpck = get_vmpck(vmpck_id, secrets, &snp_dev->os_area_msg_seqno); if (!snp_dev->vmpck) {